Vacuolar (or vacuolar-type or V-type) (H+)-ATPases have been described as “a universal proton pump of eukaryotes” (Finbour and Harrison, Biochem. J., 324, 697-712 (1997)). Vacuolar-type (H+)-ATPases are present in many tissues and cells of the body. Intracellular vacuolar (H+)-ATPase activities are present in certain organdies, and are responsible for maintaining the internal acidity thereof. This maintenance is essential for a variety of physiological functions such as: sorting of membrane and organellar proteins; proinsulin conversion; neurotransmitter uptake; cellular degradative processes; and, receptor cycling. See Mellman et al., Ann. Rev. Biochem., 55, 663-699 (1986); Forgac, Physiological Rev., 69, 765-796 (1989); Stevens and Forgac, Annu. Rev. Cell. Dev. Biol., 13, 779-808 (1997); Nelson, TIPS, 12, 71-75 (1991).
Vacuolar-type (H+)-ATPase activity is also located within specialized plasma membranes. Important examples include the vacuolar-type (H+)-ATPase activity in the plasma membranes of kidney intercalated cells, osteoclasts and sperm cells. See Stone and Xie, Kidney Int., 33, 767-774 (1988); Vaananen et al., J. Cell, Biol., 111, 1305-1311 (1990); Blair et al., Science, 245, 855-857 (1987); Wang and Gluck, J. Biol. Chem., 265, 21957-21965 (1990); Hall and Chambers, Inflamm. Res., 45, 1-9 (1996); Hall and Schaueblin, Bone and Mineral, 27, 159-166 (1994); David and Baron, Exp. Opin. Invest. Drugs, 4, 725-740 (1995); Wassarman, Science, 235, 553-560 (1987); Nelson, TIPS, 12, 71-75 (1991).
Because of the importance of vacuolar-type (H+)-ATPase activity in the maintenance of many physiological functions, compounds which inhibit vacuolar-type (H+)-ATPase will have useful pharmacological applications in a variety of different situations. See reviews by Nelson, TIPS, 12, 71-74 (1991), and Keeling et al., Ann. New York Acad. Sci., 834, 600-608 (1997), and references contained therein. For example, a given vacuolar-type (H+)-ATPase inhibitor may have utility against one or more disease states or physiological functions, in which it is desirable to inhibit an intra-organellar, vacuolar-type (H+)-ATPase-mediated process, such as acidification, accumulation of a neurotransmitter, receptor turnover, lysosomal storage, and the like. See Mellman et al., Ann. Rev. Biochem., 55, 663-699 (1986); Forgac, Physiological Rev., 69, 765-796 (1989); Stevens and Forgac, Annu. Rev. Cell. Dev. Biol., 13, 779-808 (1997); Nelson, TIPS, 12, 71-75 (1991). Similarly, a given vacuolar-type (H+)-ATPase inhibitor may be useful against one or more disease states or physiological functions, in which it is desirable to modify a plasma membrane vacuolar-type (H+)-ATPase-mediated process, such as urinary acidification, bone resorption, or the acrosomal acid secretion required for fertility. See Stone and Xie, Kidney Int., 33, 767-774 (1988); Vaananen et al, J. Cell. Biol., 111, 1305-1311 (1990); Blair et al., Science, 245, 855-857 (1987); Wang and Gluck, J. Biol. Chem., 265, 21957-21965 (1990); Hall and Chambers, Inflamm. Res., 45, 1-9 (1996); Hall and Schaueblin, Bone and Mineral, 27, 159-166 (1994); David and Baron, Exp. Opin. Invest. Drugs, 4, 725-740 (1995); Wassarman, Science, 235, 553-560 (1987); Nelson, TIPS, 12, 71-75, (1991).
Compounds that inhibit vacuolar-type (H+)-ATPases also will have important utility for cancer therapy. For example, there is literature evidence indicating involvement of vacuolar-type (H+)-ATPases in processes related to cellular proliferation, angiogenesis, tumor cell invasiveness, metastasis, and drug resistance (see, e.g., Akifusa et. al., Exp. Cell Res., 238, 82-89 (1998); Altan et al., J. Exp. Med., 187, 1583-1598 (1998); Gerard et al., J. Exp. Biol., 201, 21-31 (1998); Ishii et al., J. Antibiot., 48, 12-20 (1995); Moriyama et al., J. Biochem., 115, 213-218 (1994); Ohkuma et al., In Vitro Cell Devel. Biol., 29A, 862-866 (1993); Perona et al., Nature, 334, 438-440 (1988); Montcourrier et al., J. Cell Sci., 107, 2381-2391 (1994); Montcourrier et al., Clin. Exp. Metastatis, 15, 382-392 (1997); Martinez-Zaguilan et al., Ann. NY Acad. Sci., 671, 478-480 (1992); Martinez-Zaguilan et al., Am. J. Physiol., 265, C1015-C1029 (1993); Martinez-Zaguilan et al., J. Cell. Physiol., 176, 196-205 (1998); Nishihara et al., Biochem. Biophys. Res. Commun., 212, 255-262 (1995); Manabe et al., J. Cell Physiol., 157, 445-452 (1993); Kinoshita et al., FEBS Lett., 337, 221-225 (1994); Kinoshita et al., FEBS Lett., 398, 61-66 (1996); Ohta et al., Brit. J. Cancer, 73, 1511-1517 (1996); Ohta et al., J. Pathol., 185, 324-330 (1998); Marquardt et al., J. Natl. Cancer Inst., 83, 1098-1102 (1991); and Banderra et al., Int. J. Oncol., 12, 711-715 (1998)). Therefore, compounds that inhibit these phenomena will be useful in cancer chemotherapy.
Among the numerous challenges faced by medicinal chemistry research is the challenge of identifying new vacuolar-type (H+)-ATPase-inhibitory leads applicable to medical treatments. In addition, the identification and development of new leads useful in cancer chemotherapy remains a perplexing problem. Purely synthetic approaches toward the identification of novel anticancer agents and vacuolar-type (H+)-ATPase inhibiting agents have been typically unsuccessful, partly due to the technological and human limitations inherent in laboratory synthesis. Although biological metabolites provide a vast resource of new structurally diverse chemical compounds, the number of agents available for exploiting therapeutic opportunities are relatively few, particularly inhibitors of vacuolar-type (H+)-ATPase. For example, structural types that potently and selectively inhibit vacuolar-type (H+)-ATPases have thus far been limited to compounds such as bafilomycins, concanamycins, and benzolactone enamides such as the salicylihalamides and lobatamides (see Boyd, PCT International Patent Application No. PCT/US00/05582). Thus, there remains a need for new vacuolar-type (H+)-ATPase inhibitors and anticancer compounds, pharmaceutical compositions, and methods of using them. The present invention provides such compounds, compositions, and methods. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.